In a bowl, mix together flour, cornstarch, salt, baking soda, and cinnamon. Set aside.
In the bowl of a stand mixer (or using a hand mixer), cream together butter and both sugars on medium speed until light and fluffy (2-3 minutes). With the mixer on low, add egg and vanilla. Return mixer to medium and mix until incorporated. Scrape sides as needed.
With the mixer back on low, add dry ingredient mixture gradually until dough forms. Stir in chocolate chips and pecans by hand. Refrigerate dough for at least 30 minutes. Preheat oven to 350°F and line baking sheets with parchment paper or Silpat and set aside.
Form balls from approximately 1 tablespoon of dough. Bake for 9-11 minutes or until edges are just barely golden. Remove from oven and let cool for a couple of minutes on baking sheet before removing and placing on wire rack to finish cooling. Store in airtight container.